The virus does not distinguish between reasons for people gathering. Either it is safe or it is not safe. If it is killing grandma to gather for one reason, it's killing grandma for all reasons. If it's safe to gather for one reason, it's safe to gather for all reasons.
The Constitution guarantees the right of the people to peaceably assemble. When there are extreme circumstances, that right can be temporarily restricted, but the government does not get to decide based on whether they like or dislike the reason.